Momentum Sources and Sinks
The flow velocity, u (SI unit: m/s), at a boundary is coupled to the total mass flux of the species at the electrode surface in the following way
(6-75)
where ρ (SI unit: kg/m3) is the density of the flowing media, n the surface normal and ni is the mass flux of species i.
For flow interfaces solving for the velocity field, no-slip conditions are applied at the electrode surface, resulting in
(6-76)
where Mi (SI unit: kg/mol) is the species mass and Ni (SI unit: mol/(m2·s)) the molar flux calculated by Faraday’s law.
For a porous electrode the sum of all mass fluxes are added to the conservation equation according to:
(6-77)
Note that because the mass is usually not conserved within the species transporting phase (the right-hand side above being nonzero), the velocity field is not divergence free.